Introduction to Embedded Systems

Copyright © 2012 Embedded Systems

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Introduction To ES

Mohamed Abd Elhay


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Embedded Systems

Embedded Systems Applications

Embedded Systems Types

Memories

Embedded system developing

Embedded Systems Market in Egypt

Copyright © 2014Embedded Systems

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•Embedded system is a special purpose system designed to

perform one or a few dedicated

functions.

• Embedded systems are computing systems with tightly

coupled hardware and software integration.


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The Word “Embedded” reflects the fact that these systems are

usually an integral part of

a larger system, known as the embedding system.

“A computer built into a system and not seen by the user as

being a computer”

It is usually Embedded as a part of a complete device

including hardware and mechanical parts.


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Can Personal Computer be considered as an Embedded

System as it integrates hardware and software to

perform functions? Why?

NO

PC cannot be considered as an embedded system

because

1. It uses a General-Purpose Processor

2. The system is built independently from the software

runs on it.

Else ATM machine


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Communication:

Mobile Handsets

Switches and Routers

Image processing and Consumers:

Cameras

Mp3 and Mp4 players

PlayStation

Automotive:

Engine Management System

Claimant Control System

Appliances:

Microwave

Washing Machines


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1) Microprocessors.

2) Microcontrollers.

3) DSPs.


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o CPU = ALU + Registers + Control unit

o Microprocessor function is to fetch the instructions

from the memory then decode and execute them.

o Microprocessor alone is useless


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CPU design divide into three parts:

o The datapath

does all of the actual data processing

o A control unit

uses the programmer’s instructions to tell the datapath what to do

o An instruction

set is the programmer’s interface to CPU


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Control Unit

and

Datapath

Control Unit and Datapath


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o The hardware part of the processor that

performs the processing operations.

o Contain from Three Parts:

Computations ALU

Fast temporary storage Register file

Large memory storage RAM


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o programs with the data-path :

converts program instructions into control

signals for data-path.

Executes program instructions in the correct

sequence.

DA AA BA MB FS MD WR

V C N Z

Branch

Control

ADRS

Instruction

RAM

OUT

Instruction Decoder

PC


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• CPU = ALU + Registers + Control unit

W R

DA

AA B A

FS V C N Z

MB

MD

MW

constant

DA AA B A MB FS MD W R M W

V C N Z

Branch

Control

PC

ADRS

Instruction

RAM

OUT

Instruction Decoder

D

Register file

A B

1 0

Mux B

ADRS DATA

Data RAM

OUT

A B

ALU

G

0 1

Mux D

Control Unit Datapath


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Harvard arch.:

includes two memory units :

o An instruction memory holds the program

o A separate data memory is used for computations

o The advantage is that we can read an instruction and load or store data in the same clock cycle

Von Neumann arch.:

includes one memory unit :

o a single main memory that holds both program instructions and data


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RISC CISC

Reduced Instruction Set Computer Complex Instruction Set Computer

optimize execution of instructions by

single instruction limiting capabilities

integrate several functionalities in one

instruction

The compiler or programmer

synthesizes complicated operations

by combining several simple

instructions. (ex: divide operation)

The Compiler is simple as has wide verity of

instructions to perform the complicate

operation


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:

RISC CISC

simple operations that can each

execute in a single cycle

the instructions are often take many cycles to

execute.

have a large general-purpose register

set.

dedicated registers for specific purposes

Any register can handle with ALU dedicated registers specific for ALU operation

ALU can‟t deal with Memory directly ALU can deal with memory directly

Due to Memory accesses are costly :

the core can operate at higher clock

frequencies.

and operate at lower clock frequencies

Separate load and store instructions

transfer data between the register bank

and external memory are needed to all

ALU operations

Separate load and store instructions transfer

data between the register bank and external

memory aren’t needed to all ALU

operations

Helps to pipeline execution of instructions


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:

• Microcontroller = CPU + Memory + Peripherals

•Designed for standalone operation.


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:

Microcontroller Main Components

Microcontroller has eight main components:

1. Central processing unit (CPU)

2. ROM

3. RAM

4. Input and Output (GPIO or DIO)

5. Timer

6. Interrupt circuitry

7. Buses

8. Watchdog


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• Like microcontrollers BUT Focus on very efficient execution of

arithmetic operations.

• DSP has :

o specialized arithmetic units,

o optimized design in the memory,

o Addressing and bus architectures with multiprocessing capability

that allow the DSP to perform complex calculations extremely fast

in real time.

• Used widely in digital signal processing in communications systems

such as Cell phones and Image and video processing.

• TI (Texas Instruments) has been the dominant player in the DSP market

for several years.


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Multi-core system on chip

Like mobile handset which has one chip contains:

o DSP processor

o Embedded processors like ARM

o Custom hardware for GSM

o Custom peripherals for board interface (keyboard,

touch screen, memory card interface)


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1-Program Memory

MROM • Masked ROM

• Programmed by the manufacturer.

• The term „masked‟ comes from the manufacturing process

• In case of a large-scale production, the price is very low.

PROM • Programmable rom

• Also called One time programmable ROM

• enables programmer to download a program into it one time only.

• If an error is detected after downloading, the only thing you can do is

to download the correct program to another chip.


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1-Program Memory

UV EPROM • UV Erasable Programmable ROM

• It enables data to be erased under strong ultraviolet light.

• After a few minutes it is possible to download a new program.

EEPROM • ELECTRICALLY ERASABLE PROGRAMMABLE ROM

• can be erased by exposing it to an electrical charge

Flash Memory • Invented in the 80s in the laboratories of INTEL

• Represented as the successor to the UV EPROM.

• Can be written and cleared practically an unlimited number of times,

• most microcontrollers are manufactured in flash technology.


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2-Data Memory

SRAM: • Static random access memory

• uses multiple transistors, typically four to six, for each memory cell

• doesn't have a capacitor in each cell.

DRAM: • Dynamic random access memory

• has memory cells with a paired transistor and capacitor requiring

constant refreshing.


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Trade off between HW and SW

For a certain application

o Which functional blocks should be performed in Hardware??

o Which functional blocks should be performed in software??


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Software characteristics

o Highly configurable

o Shorter development cycle

o Easier in versions updates

o Cheaper

o Constrained with processor speed which may satisfy real time

application and may not


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Hardware characteristics

o Longer development cycle

o Customized for specific application

o Better performance in high speed real time application


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Board

SYSTEM ON BOARD


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SYSTEM ON CHIP

Keyboard

controller USB interface

Memories CPU

Customized

hardware

LCD

controller

ASIC Chip


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• In complicated systems functional blocks could be:

o Level 1: External discrete hardware component on board.

o Level 2: Hardware integrated with CPU on chip (SoC).

o Level 3: Done by software running on CPU.

HW / SW Partitioning


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“Those systems in which the correctness of the system

depends not only on the logical result of the computation, but

also on the time at which the results are produced”

Real Time Systems are a very fast systems?

Real-time means completing tasks within specified deadlines,

it is not defined or limited by a specific execution speed.


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System Development Cycle

1. System Specification Analysis

2. System Design

3. Development

Hardware Development

Software Development

4. System Integration

5. System Validation


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Software Development Cycle

1-Software Specification

2-Software Design

3-Coding / Testing

4-Software Integration

5-Software Validation


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1- Assembly

a-Lowest level human readable

b-Platform specific.

c-Assembly has one-to-one corresponding machine language

d-Using compiler to convert High Level language to Assembly

2-C Language


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References

• ESC Training Team


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[email protected]

Introduction to Embedded Systems

Technology